Answer:
28/9
Step-by-step explanation:
If the roots are J and K, then:
3 (x − J) (x − K) = 0
3 (x² − (J+K)x + JK) = 0
So if we factor out the leading coefficient:
3x² − 2x − 4 = 0
3(x² − 2/3x − 4/3) = 0
The coefficient of the second term is the sum of the roots:
J + K = 2/3
And the constant is the product of the roots:
JK = -4/3
If we take the sum of the roots and square it:
(J + K)² = (2/3)²
J² + 2JK + K² = 4/9
And subtract twice the product:
J² + K² = 4/9 − 2JK
J² + K² = 4/9 − 2(-4/3)
J² + K² = 4/9 + 8/3
J² + k² = 28/9
